Fiber supply method and apparatus in an open-end spinning system utilizing airflow and centrifugal force

ABSTRACT

Disclosed herein is a method and apparatus for use with yarnspinning equipment wherein individual fibers are extracted from a bundle of fibers delivered from a supply source at a position in a fiber supply device where the fluid speed of the airstream for conveying the fibers is maximum, while the bundle of fibers is still gripped by the supply source. In the present invention, a distance between the nip point of the supply source and the above-mentioned position is particularly defined with respect to the staple length of the spinning material. Furthermore, preferable shapes are illustrated for the fiber guide conduit, the fiber-separating passage, and the fiber supply conduit of the fiber supply device for producing a high quality yarn.

United States Patent [32] Priority Jan. 30, 1968, Jan. 30, 1968, Mar. 4, 1968,

Mar. 11, 1968 [33] Japan [31] 1 43/5657, 43/5658, 43/ 13610 and [54] FIBER SUPPLY METHOD AND APPARATUS IN AN OPEN-END SPINNING SYSTEM UTILIZING AIRFLOW AND CENTRIFUGAL FORCE 6 Claims, 14 Drawing Figs.

[52] U.S.Cl 57/58.89, 57/156,57/5895 [51] Int. Cl r. D0lh 1/12 [50] Field of Search 57/58. 89-58.)5. I56

[56] References Cited UNITED STATES PATENTS 2,773,282 12/1956 Backer 57/5893 3,115,001 12/1963 Cizek etal. 57/5893 FOREIGN PATENTS 6,711,373 2/1968 Netherlands 57/5895 Primary Examiner-John Petrakes AttorneysRobert E. Burns and Emmanuel J. Lobato ABSTRACT: Disclosed herein is a method and apparatus for use with yarn-spinning equipment wherein individual fibers are extracted from a bundle of fibers delivered from a supply source at a position in a fiber supply device where the fluid speed of the airstream for conveying the fibers is maximum,

while the bundle of fibers is still gripped by the supply source.

In the present invention, a distance between the nip point of the supply source and the above-mentioned position is particularly defined with respect to the staple length of the spinning material. Furthermore, preferable shapes are illustrated for the fiber guide conduit, the fiber-separating passage, and the fiber supply conduit of the fiber supply device for producing a high quality yarn.

PATENIEU SEP 1 4|91| SHEET 1 OF 4 FIBER SUPPLY METHOD AND APPARATUS IN AN 'OPEN- END SPINNING SYSTEM UTILIZING AIRFLOW AND CENTRIFUGAL FORCE The present invention relates to a fiber supply method and device for use in a spinning system utilizing airflow and centrifugal force, and, more particularly, it relates to a method for supplying a continuous bundle of fibers from a fiber supply source to a high-speed spinning rotor, wherein the bundle of fibers is first shredded to provide. individual fibers which are carried with a high-speed airstream from the supply source to an inside wall of the rotating rotor.

Attempts have been made in the past to develop a spinning method or equipment utilizing airflow and centrifugal force for practical industrial production of yarns. The above-mentioned known spinning equipment comprises means for supplying a continuous bundle of fibers from a high-speed supply source to a rotor, so that the bundle of fibersis shredded into numerous individual fibers when the fibers are carried together with an airstream flowing toward the inside wall of the rotor, and so that the shredded fibers are accumulated in the inside wall of the rotating rotor successively by an action of the centrifugal force and airflow; and, means for stripping the accumulated fibers from the inside wall of the rotor, and for twisting the bundle of fibers when the accumulated fibers are stripped from the rotor and carried to a takeup roller.

It has been noticed that the above-mentioned means for supplying a continuous bundle of fibers is a very important element of a spinning system of this type, since the shredding action has a profound effect on the quality of the yarn. To attain the above-mentioned supply means function, it is desirable to have the maximum speed of the airstream at a location just before leaving a nip point of the supply source of the bundle of fibers so as to shred the bundle of fibers to permit them to be separated from each other, thereby allowing the individual fibers to be carried together with the airstream in their separated state.

If the above-mentioned shredding action is insufficiently impartedto a certain number of fibers in a stationary condition upon the inside wall of the rotating rotor, and consequently yarn breakage becomes unavoidable and the yarn produced hasan uneven thickness with slubs and neps. The rincipal object of the present invention is toprovide a method and apparatus for. supplying a bundle of fibers in a condition wherein the yarn may be spunin a steady and highly efficient manner while shredding the bundle of fibers into separate individual fibers.

A further object of the present invention is to provide a practical device for supplying a uniform amount of individual fibers, from a bundle of fibers, to a rotating rotor while controlling the speed of the suction airstream.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings to which the scope of the invention is in no way limited.

FIG. lis a sectional view of the main portion of spinning equipment provided with an embodiment of the supply device according to the present invention,

FIG. 2 is a sectional view of the supply device shown in FIG.

FIG. 3 is an explanatory diagram showing the variation curve of the fluid speed of the airstream in the supply device shown in FIG. 1,

FIG. 4 is an enlarged sectional view of the entrance portion of the supply device shown in FIG. 1,

FIGS. 5A and 5B are explanatory diagrams showing the variation curve of the fluid speed of the supply device in connection with the particular shape of the passage shown in this drawing,

FIG. 6 is an explanatory staple diagram showing the shape of individual fibers carrying through the passage of the supply device,

FIG. 7 is a sectional view of another embodiment of the supply device according to the present invention,

FIG. 8A is a sectional view of the supply device, taken along line VIIlA-VIIIA, shown in FIG. 7,

FIG. 8B is a sectional view of a supply device, similar to the device shown in FIG. 7, taken in the same way as the drawing of FIG. 8A,

FIG. 8C is a sectional view of the supply device, taken along line VIIICVIIIC, shown in FIG. 7,

FIG. 8D is a sectional view of a supply device, similar to the device shown in FIG. 7, taken in the same way as the drawing of FIG. 8C,

FIG. 9 is a sectional view of another embodiment of the supply device according to the present invention,

FIG. 10 is an explanatory view of the passage of the supply device shown in FIG. 9.

Generally, according to the supply device, for spinning equipment using an airstream, of the present invention, a bundle of fibers is continuously fed into a supply device so as to convey the fibers to an inside wall of a spinning rotor while shredding the bundle of fibers into separated individual fibers. As a plurality of fibers accumulated upon the inside wall of the rotor is taken out, they are twisted to produce yarn. In particular the fibers are extracted from the bundle at a distance L between a nip point of the fiber supply source and a particular position in a fiber supply passage of the device where thefluid speed of the airstream is maximum, said distance being less than the average fiber length of the spinning material, and greater than two-thirds of the average fiber length of the spinning material.

The above-mentioned limitation of the supply device according to the present invention is hereinafter illustrated in more detail. Referring to FIG. I, a bundle of fibers l, which is delivered from a pair of delivery rollers 2a, 2b and fed into a fiber guide conduit 3 of the supply device, is shredded to form individual fibers which are separated from each other in such a way that an individual fiber is drawn from the bundle of fibers while being conveyed in a fiber-separating passage 4. Next, the individual fibers are conveyed by an airstream through a fiber supply conduit to a spinning rotor the inside wall of the rotor 6. Then, a plurality of fibers accumulated upon the inside wall of the rotor 6 are stationarily taken out of the rotor, at a point on the rotational axis thereof, while twisting them so as to form a yarn 7 which is taken up by a pair of takeup rollers 9a, 9b after passing through a discharge pipe 8, whereupon a yarn package is made by a winder (not shown).

To attain the object of the present invention, the abovementioned supply device of the present invention is provided with a particular construction as illustrated in the drawings. That is, referring to FIG. 2, the supply device of the invention is connected to a compressed-air source, disposed outside of the spinning equipment, by way of anair supply conduit 11, and the compressed air supplied through the conduit II, and the compressed air supplied through the conduit 11 is ejected from a cylindrical slit 10 at a position adjacent to an outlet 13 of the fiber guide conduit 3 after passing through a cavity 12. Consequently, the air pressure in the fiber guide conduit 3 becomes negative in accordance with the ejecting effect caused by the jetstream of the air from the circular slit l0, and the bundle of fibers I delivered from the delivery rollers 2a and 2b is fed through the fiber guide conduit 3 by the suction force of the airstream. The bundle of fibers is shredded into individual fibers, separated from each other at a position adjacent to the outlet 13 of the fiber guide conduit 3 and the fiber-separating passage 4, and the individual fibers are then blown to the inside wall of the rotating spinning rotor 6. At the position adjacent to the outlet I3 of the fiber guide conduit 3, the jetstream from the circular slit 10 causes a pulling force of the fibers from the bundle of fibers l and a force for separating the fibers from each other. In the above-mentioned spinning method, to produce high quality yarn, it is desirable after shredding the bundle of fibers, to supply the individual fibers into the rotating spinning rotor in a uniform and stational condition as illustrated in FIG. 1. It must be recognized in particular, that it is more important to shred the bundle of fibers into individual fibers rather than to convey separated fibers with the airstream. Further, it is preferable to use a lesser quantity of compressed air with lower pressure.

By careful laboratory tests, the following results were obtained:

I. In the case L 1, where L represents the distance between the nip point of the fiber supply source and a particular position in a fiber supply passage of the device where the fluid speed of the airstream is maximum, and l represents the average fiber length: Hence, the bundle of fibers is carried by the suction airstream having its maximum fluid speed just after leaving the nip point of the fiber supply source, and the shredding of the bundle of the fibers into the individual fibers is so insufficient that the separation of the fibers is also insufficient to supply the fibers to the rotating rotor continuously. Further in the above-mentioned condition, the arrangement of the fibers is disheveled by the high-speed airstream while passing through the fiber-separating passage 4, and the fibers are conveyed to the inside wall of the rotor 6 in an irregular condition. Therefore, the yarn breakage during the spinning operation increases remarkably, and only slubby yarn can be produced.

2. In the case of M; L 1, the forward end portion of the bundle of fibers is exposed to the airstream of maximum fluid speed at the outside of the fiber guide conduit while the rear end portion of the bundle of fibers is still gripped by the nip of the delivery rollers 2a, 2b. Therefore, the forward end portion of the bundle of fibers is fully opened in the above-mentioned condition, and individual fibers are extracted from the bundle one by one so that they are conveyed to the inside wall of the rotating spinning rotor 6 after passing through the fiber supply conduit 5. This is the ideal condition for supplying the spinning material to the spinning rotor 6.

3. In the case of L %l, the forward end portion of the bundle of fibers is exposed to the airstream of maximum fluid speed at the outside of the fiber guide conduit while the rear end portion of the bundle of fibers is still gripped by the nip of the delivery rollers 2a, 2b. However, the above-mentioned condition is still maintained even after the forward end portion of the bundle of fibers passes through the fiber-separating passage because the rear end portion of the bundle of fibers is still gripped by the nip of the delivery rollers 20, 2b. Consequently, the forward end portion of fibers which are opened by the airstream tend to entangle with each other, and it is quite possible to produce a neppy yarn.

As is clear from the above-mentioned illustration and the following examples, the distance L must be in a range from two-thirds times of the average fiber length to the value below the average fiber length for imparting the effective shredding action to draw individual fibers from the bundle of fibers one by one.

EXAMPLE I In the spinning equipment shown in FIGS. I and 2, the distance S between the entrance of the fiber guide conduit 3 of the fiber supply device and the nip point of the delivery rollers 2a, 2b was set as mm., the distance L between the nip point of the above-mentioned delivery rollers and the position of the fiber supply device where the fluid speed of the air stream was maximum is set as onehalf or, two-thirds or, four-fifths or,

' one or, four-thirds times of the average fiber length l, and the diameter of the conduit for passing the airstream at the abovedefined position of the supply device was set as 2.5 mm. so as to attain the maximum fluidspeed of the airstream of 120 m.p.s.

A roving composed of polypropylene staple fiber (fineness l.5d, staple length 38 mm.) was drafted at the draft ratio of 25 by a fiber supply source, and the drafted bundle of fibers was supplied to the above-mentioned spinning equipment, whereby the result shown in table I was obtained. The conveying condition of the fibers in the fiber supply device was observed during the spinning operation. In this spinning block the yarn count in cotton system is 30" the twist multiplier was 5.0. the air pressure of the supplied air was 0.4 kg./cm., and the air capacity applied for this test was lOI/min.

As shown in table 1, the preferable conditions are observed in the test of Test No. 2, 3 and 4, in other words, the distance L must be preferably set in the range -;lL l, to produce yarn having good quality with high-spinning efficiency.

EXAMPLE 2 By using the spinning equipment shown in FIG. 1, a spun yarn was produced from a roving composed of acrylic staple fiber (fineness 1.5 denier, fiber length 38 mm.), under the following conditions:

Thickness of the roving I grain/l5 yam Total draft ratio of the supply source Delivery speed of the delivery roller of the supply source 55 m./min. Yarn count 30" Take up speed 48 m./min. Rotating speed of the rotor 30,000 r.p.rn. Pressure of the supply air 0.4 kgJcm. Capacity of the supply air l0 Llmin.

Distance L 35 mm. Distance S l3 mm. Maximum fluid speed of the airstream I30 mJsec.

In the above-mentioned spinning test, the yarn breakage during the spinning operation is 58/],000 sp. hr., and the evenness of the yarn in U percent (normal test) was 10.6 percent. To estimate the quality of yarn produced by the apparatus of the present invention, another acrylic fiber yarn composed of the same material as the present example was produced by the conventional ring-spinning system from the same roving as the present example. The yarn count was also 30" and its U percent was 11.5 percent. Therefore, it can be confirmed that the evenness of the yarn according to the present invention is superior to that of the conventional yarn. Furthermore, by means of a high-speed camera, the desirable conveying condition of fibers in the supply device of the invention was observed.

To aid the understanding of the variation of the fluid speed in the fiber supply device, an experimental result is shown in FIG. 3. In this experiment, the above-mentioned distance S is set as 13 mm., and it is observed that the distance between the entrance of the fiber guide conduit and the position of the fiber supply device where the fluid speed of the airstream is maximum is 21 mm., consequently, the distance L is 34 mm. As the average fiber length is 38 mm., the distance L is represented as 17/191.

As already described, a principal condition for producing the high-quality yarn having a low breakage rate by the abovementioned spinning equipment, is that a bundle of fibers supplied from a supply source such as a draft device must be conveyed into the fiber supply device smoothly. It is also necessary that the bundle of fibers is shredded into individual fibers separated from each other, while passing through the fiber supply device and that individual fibers are extracted from the bundle of fibers one by one so as to be blown to the inside wall of the rotating spinning rotor ln the above-mentioned conditions, the compressed air must be effectively applied to develop the airstream of the desired condition in the fiber supply device. To increase the force necessary to draw a bundle'of fibers into the fiber guide conduit of the fiber supply device, and to ensure the parallel condition of fibers in the airstream, it is desirable to make the inside diameter of the fiber guide conduit as small as possible while still permitting a bundle of fibers supplied from the supply source to be drawn smoothly into the fiber guide conduit. However, mill tests have shown that it is quite possible to accumulate fibers at the entrance of the fiber guide member, thereby causing breakage of the yarn or there is a certain difficulty in drawing a bundle of fibers into the fiber guide conduit at the time of restarting the spinning operation after stopping the supply of fibers to the device when the yarn is broken.

By our many experiments, the fiber guide conduit of the fiber supply device is preferably trumpet-shaped with a crosssectional diameter, in addition to the above-mentioned limitation of the distance L. Referring to FIG. 4, when the inside diameter of the fiber supply conduit 3 is designated as d, while the diameter of the entrance of the conduit 3 is designated as D, and the distance between the outside surface of the entrance and a terminal of the trumpet-shaped entrance is represented as m, the following conditions are desirable to solve the trouble caused by the accumulation of fibers upon the s? sith fihs sl d; Q B hEP 4 D Z 1.

The above-mentioned condition can be applied for using the fiber guide conduit provided with a tapered conduit.

The above-mentioned effect caused by selecting the shape of the fiber guide conduit 3 is more clearly shown by the following experiment. In FIG. 5A, two different types of conduits a and b are shown. The detailed dimension of the conduits a and b are shown in table 2.

The above-mentioned fiber guide conduits are applied to the fiber guide device shown in FIG. 1 respectively, and polypropylene yarn is spun by the following spinning condition shown in table 3.

TABLE 3 Spinning material used Polypropylene staple fiber Fineness staple length l.$d X 38 mm.

The supplied bundle Drafted roving of grain] of fibers l5 yarn by draft ratio 21.5

Delivery speed of the According to the above-mentioned spinning test, fibers tend to accumulate at the entrance of the fiber guide conduit 3 because of the weak suction force in the conduit 3 in case of applying the conduit of type b, while a bundle of fibers supplied from the delivery roller 2a, 2b is very smoothly drawn into the conduit 3 without any accumulation in the conduit. In FIG. 5B, showing the variation of the fluid speed of the airstream in the conduits of type a and b, it is clear that the force to draw the bundle of fibers at the entrance of the conduit 3 of type a is remarkably stronger than that of type b, in spite of the same diameter of the entrance as that of type b. Consequently, the bundle of fibers can be drawn by the air pressure into the fiber supply conduit 3 and disposed at a stationary position. Also, it is desirable that the inside diameter of the fiber-separating passage 4, succeeding to the fiber guide conduit 3 be uniform, and the fiber supply conduit 5, succeeding to the fiber-separating passage 4, be spread out toward the outlet of such conduit 5.

By our many experiments, it was found that the yarn breakage during the spinning operation can be remarkably reduced by coating the inside walls of the fiber guide conduit 3 and the fiber-separating passage 4 with polytetrafluoroethylene resin. That is, it is necessary to decrease the frictional resistance of the fibers to the inside wall of the fiber guide conduit 3 and the fiber-separating passage 4 for reducing the yarn breakage during the spinning operation. On the contrary, if the inside walls of the abovementioned passages are provided with a roughened surface, certain undesirable components such as lamps of fibers, fiber drafts, or or oiling agents, etc. causes the hook formation of fibers, thereby fibers tend to entangle each other and the smooth conveying of the fibers becomes impossible. To prevent the above-mentioned drawback, the polytetrafluorethylene resin is preferably applied with a coating thickness in a range between 10 and 60 u, and if the coating thickness is thinner than the above-mentioned value, socalled pinholes are produced in the coating, thereby the above-mentioned drawback can not eliminate. Further, the coefficient of friction, of the inside wall of the passage to the fiber, after the above-mentioned coating has been applied, decreases, for example, to 0.17 in case of the yarn speed of 50 m/min.

EXAMPLE 3 In the spinning equipment shown in FIG. 1, the inside wall of the fiber guide conduit 3 and the fiber-separating passage 4 were coated by polytetrafluoroethylene resin with 20 thickness. Before the coating treatment, the inside walls of the conduit 3 and the passage 4 were cleaned by a certain chemical agent. Polypropylene staple fiber (fineness 1.5 denier, staplc length 38 mm.) was used for this experiment. The air pressure of the supplied air was 0.4 to 0.5 kg./cm. The conveying condition of fibers was observed by using a stroboflash device and the yarn was produced and studied with regard to its quality.

ln the above-described experiment, it was observed that the fibers were conveyed in a desirable condition, and no carrying of lumps of fibers was observed. The quality of yarn produced in this test together with the comparative yarns are shown in table 4. To make clear the hook formation of the yarns, staple diagrams are analyzed for the yarn C according to the present experiment, yarn B produced by the spinning equipment of the invention but without the above-mentioned coating treatment, and yarn A produced by the conventional ring-spinning system. The fibers for making the staple diagram are prepared by after cutting the yarn at 20 mm. intervals, and then the cut yarn is untwisted so as to prepare a group of fibers of 100 mg. The original staple length of the spinning material is 38 mm. In FIG. 6 showing the three staple diagrams, fibers having longer length than 20 mm. are observed. The existence of these long fibers discloses the existence of hooks within the yarn.

In the above-mentioned staple diagram, the ordinate represents fiber length" in millimeter, while the abscissa represents distance from the origin of the staple diagram" in centimeter.

As is clearly shown in table 4 and FIG. 6, the yarn C produced by the coated device shows better quality than the yarn B. The number of fibers having longer length than 20 mm., that is number of hooks contained in the yarn, of the yarns B and C is greater than that of yarn A, and it is shown that the tensile strength of the yarns B and C is almost 10 percent weaker than that of the yarn A. And it was observed that the yarn breakage during the spinning operation is remarkably reduced by using the coated device, whereby the yarn quality and spinning efficiency are also improved by the above-mentioned coating treatment.

In the experiments, it was found to be preferable that the shape of the fiber passage composed of the fiber guide conduit and the fiber-separating passage be provided with at least a portion having a flattened cross section such as elliptical or rectangular, rather than the circular cross section, particularly at the entrance of the fiber guide conduit. This is particularly effective in case of applying the conventional roller draft for the fiber supply source. In other words, it was found that, by means of avoiding the influence of the transverse motion of the fleece supply means of the fiber supply source, the shredding of the bundle of fibers into the individual fibers and the extraction of individual fibers from the bundle of fibers are more effectively achieved with this structure. In fact, the maximum width of the transverse motion is almost 6 mm. in the conventional ring-spinning frame for producing the cotton yarn; however, by means of utilizing the above-mentioned fiber guide conduit, the airstream in the conduit can be maintained stationary, and the conveying speed of the fibers together with the airstream can be controlled so as to obtain good yarn quality.

The above-mentioned function of the fiber guide conduit is illustrated in detail with reference to FIG. 7. That is, the fiber passage comprises a fiber guide field 14 and a fiber separation field 17 so as to form a passage for conveying fibers. Referringto FIGS. 8A, 8B, 8C and 8D, X-Y coordinates are considered in a cross-sectional plane of the passage, and the long axis a and short axis b are also considered in the X and Y coordinates respectively, the ratio b/a of the cross section of the passage is set in a range below 1, in other words, b/a l. Any shape of the cross sections of the passage may be applied for the fiber guide conduit of the present invention if the abovementioned condition (b/a 1) is satisfied. For example, the preferable elliptical and rectangular cross section of the conduits are shown in FIGS. 8A and 8B. The cross section of the conduit shown in FIG. 8C shows a cross section of the conduit, taken along line VIII-VIII, in FIG. 7, and the cross sections of the conduit at the terminal of the fiber guide field and the fiber separation field are rectangular. By means of applying the above-mentioned particular shape of the cross section, the following effect can be obtained.

1. The suction airstream of the fiber guide conduit and the airstream of the fiber separating passage can be effectively controlled.

2. In the case of applying the roller draft equipment as the fiber supply source, or the fiber supply source provided with a pair of delivery rollers, the entrance of the fiber guide conduit has sufficient width to receive the fleece having a certain width, even if the supply of the fleece has a transverse motion imported thereto. In other words, the cross section of the entrance of the fiber guide conduit is set as b/a l so as to receive the fleece without any disturbance. Further, the above-mentioned effect is hereinafter illustrated as follows. Referring to FIG. 7 and FIGS. 8C and 8D, a high-speed fluid stream f develops the secondary airstream g flowing in the same direction as stream f, and the secondary airstream g forms a suction airstream for drawing the supplied bundle of fibers into the fiber guide conduit. The strength of the airstream g can be controlled by adjusting the condition of the fluid stream f together with the above-mentioned second effect caused by the shape of the fiber guide conduit.

Concerning the cross section of the fiber guide conduit at its outlet, the following effect can be considered, that is, the conduit having the cross section shown in FIG. 8D is more effective in comparison with the conduit having the circular cross section shown in FIG. 8C with regard to conveying the bundle of fibers comprising the same number of fibers. In the case where the fiber guide conduit having a circular cross section is used, as shown in FIG. 8C, the radius of the circular cross section must be limited to a smaller value in comparison with the long axis a of the cross section of the ellipse so as to obtain the equal suction force. Further, it is found that the intervened space 21 between the inside wall of the conduit and the surface of the fibers must be constant in any conduit having a different cross section as shown in FIGS. 8C and 8D.

Referring to FIGS. 9 and 10, another embodiment of the fiber supply device provided with a modified fiber guide device is shown. In this fiber guide conduit, particular consideration is made concerning the shape of the fiber guide conduit for the stationary receiving of a bundle of fiber and the conveying of the fibers to the rotating spinning rotor, in addition to the limitation of the distance L. In the fiber supply device provided with a fiber conveying passage comprising a fiber guide conduit and fiber-separating passage succeeding the fiber guide conduit, the fiber guide conduit is spread out from a certain position to the outlet of the passage with a taper in range between 5 and 60.

Referring to FIG. 9, a bundle of fibers 1 is supplied to the fiber supply device of the invention from a pair of delivery rollers 2a, 2b. A fiber guide conduit 24 is disposed at a position adjacent to the delivery rollers 2a, 2b, and an end 28 of the fiber guide conduit 24 is connected to an air cavity 26 which is connected to the compressed air source disposed outside of the equipment as shown in the drawing. A circular slit is formed at the outside position of the outlet of the fiber guide conduit 24, and a fiber-separating passage 27 is also connected thereto. The distance L between the nip point of the delivery rollers 2, 2a and the position of the fiber-conveying passage, where the fluid pressure of the airstream is maximum, is set to conform to the above-mentioned condition. Therefore, a bundle of fibers is shredded into individual fibers separated from each other, and individual fibers are drawn from the bundle of fibers one by one at the fiber-separating passage 27 by the high-speed airstream ejected from the circular slit. The fiber guide conduit 24 is spread out at a certain position to the outlet of it by an angle 9 so as to prevent troubles caused by fiber refuse etc. Further, it is understood that since the cross-sectional area A at the outlet portion of the conduit 24 is larger than that of the cross-sectional area A, of the inlet portion while the fluid speed of the air stream is increased from U to U,, the number of conveying fibers is constanti therefore, the intervened space of the fibers in the bundle of fibers is increased, and the individual fibers can be easily drawn from the bundles of fibers one by one without entangling. As already described, the preferable angle 6 is in a range between and 60, and if 9 is larger than 60, a certain eddy current is observed in the fiber-separating passage 27 which causes an irregularity of thickness of the yarn.

By using the above-mentioned fiber guide conduit, the yarn breakage during the spinning operation is reduced and any accumulation of fibers or other impurities in the fiber guide conduit 24 is completely prevented. The preferable conveying action of the fibers by the above-mentioned guide conduit was observed by using a high-speed movie camera.

While the invention has been described in conjunction with certain embodiments thereof is to be understood that various modifications and changes may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. ln an open-end spinning system wherein fibers are supplied from a source consisting of a bundle of fibers which are separated and carried by pneumatic flow into a spinning rotor for producing yarn: a method comprising controlling the flow speed of said pneumatic flow to be a maximum at a distance L downstream of a nip point of said bundle of fibers, said distance L being defined as 4!?! r =n wherein Z is the average length of said fibers, whereby said fibers are extracted from said bundle of fibers at said point of maximum flow speed, thereby decreasing breakage and unevenness of the yarn.

2. ln open-end spinning apparatus having a spinning rotor, a fiber-supply device for supplying separated fibers from a bundle of fibers and for transporting said fibers by a pneumatic flow to said spinning rotor, and means for withdrawing said fibers from said rotor to produce a twisted yarn; an improvement wherein said fiber supply device comprises elements including a fiber guide conduit for receiving said bundle of fibers therethrough, fiber-separating means disposed downstream of said fiber guide conduit for receiving said fibers from said guide conduit, and a fiber supply conduit disposed downstream of said fiber-separating means and in communication with a fiber input to said rotor for coupling said fibers from said separating means to said rotor, said elements being arranged so that the speed of said pneumatic flow is a maximum within said fiber supply device at a distance L downstream of a nip point of said bundle of fibers, said distance L being defined as ALL wherein Z is the average length of said fibers, whereby said fibers are extracted from said bundle of fibers at said point of maximum flow speed, thereby decreasing breakage and unevenness of the yarn.

3. Spinning apparatus as set forth in claim 2, in which said fiber guide conduit is provided with an upstream opening for receiving said bundle of fibers, said opening having a trumpet shape spreading out in the upstream direction and defined by the expressions m 5 2d, and

D 5 1.541. wherein, D represents the inside diameter of the upstream extremity portion of said trumpet shape opening in said guide conduit, d represents the inside diameter of the downstream extremity of said trumpet-shape opening in said guide conduit, and m represents the axial length of said trumpet-shape opening.

4. In a spinning apparatus comprising a fiber supply device utilizing an airstream for conveying a bundle of fibers supplied from a supply source, while shredding said bundle of fibers into individual fibers; a spinning rotor for accumulating said individual fibers supplied from said fiber supply device upon an inside wall of said rotor while rotating at high speed, said rotor provided with an aperture for taking out yarn produced therein, means for stripping said accumulated fibers from said inside wall of said rotor while rotating said rotor and taking up produced yarn from said rotating rotor through said aperture; an improvement wherein said fiber supply device comprises a fiber guide conduit disposed adjacent to said supply source said fiber guide conduit having a flattened cross section in its upstream portion, fiber-separating means having an upstream inlet disposed to receive fibers from a downstream outlet of said fiber guide conduit, a fiber supply conduit disposed between said fiber-separating means and the inside of said rotor, and means for controlling the speed of said airstream to be at a maximum at a position within said fiber-separating means, said position being spaced downstream from a nip point of said fiber supply device at a distance L defined as %l i L 2 I wherein, [represents the average fiber length of said fibers.

5. In a spinning apparatus comprising a fiber supply device utilizing an airstream for conveying a bundle of fibers supplied from a supply source, while shredding said bundle of fibers into individual fibers; a spinning rotor for accumulating said individual fibers supplied from said fiber supply device upon an inside wall of said rotor while rotating at high speed, said rotor provided with an aperture for taking out yarn produced therein, means for stripping said accumulated fibers from said inside wall of said rotor while rotating said rotor and taking up produced yarn from said rotating rotor through said aperture; an improvement wherein said fiber supply device comprises a fiber guide conduit disposed adjacent to said supply source, fiber-separating means having an upstreaminlet disposed to receive fibers from a downstream outlet of said fiber guide conduit, wherein a portion of either of said fiber guide conduit and said fiber-separating means is provided with at least a portion having a flattened cross section in the path of said fibers conveyed by said airstream, a fiber supply conduit disposed between said fiber-separating means and the inside of said rotor, and means for controlling the speed of said airstream to be at a maximum at a position within said fiber-separating means, said position being spaced downstream from a nip point of said fiber supply device at a distance L defined as /31; L 2 I wherein 1 represents the average fiber length of said fibers.

6. In a spinning apparatus comprising a fiber supply device utilizing an airstream for conveying a bundle of fibers supplied from a supply source, while shredding said bundle of fibers into individual fibers; a spinning rotor for accumulating said individual fibers supplied from said fiber supply device upon an inside wall of said rotor while rotating at high speed, said rotor provided with an aperture for taking out yarn produced therein, means for stripping said accumulated fibers from said inside wall of said rotor while rotating said rotor and taking up produced yarn from said rotating rotor through said aperture; an improvement wherein said fiber-supply device comprises a fiber guide conduit disposed adjacent to said supply source, fiber-separating means having an upstream inlet disposed to receive fibers from a downstream outlet of said fiber guide conduit, a fiber-supply conduit disposed between said fiberseparating means and the inside of said rotor wherein an inside wall of said fiber supply device is coated with polytetrafluoroethylene resin, and means for controlling the speed of said airstream to be at a maximum at a position within said fiber separating means, said position being spaced downstream from a nip point of said fiber supply device at a distance L defined as 61; L 5 I wherein, 1 represents the average fiber length of said fibers. 

1. In an open-end spinning system wherein fibers are supplied from a source consisting of a bundle of fibers which are separated and carried by pneumatic flow into a spinning rotor for producing yarn: a method comprising controlling the flow speed of said pneumatic flow to be a maximum at a distance L downstream of a nip point of said bundle of fibers, said distance L being defined as 2/3 1 L l wherein l is the average length of said fibers, whereby said fibers are extracted from said bundle of fibers at said point of maximum flow speed, thereby decreasing breakage and unevenness of the yarn.
 2. In open-end spinning apparatus having a spinning rotor, a fiber-supply device for supplying separated fibers from a bundle of fiBers and for transporting said fibers by a pneumatic flow to said spinning rotor, and means for withdrawing said fibers from said rotor to produce a twisted yarn; an improvement wherein said fiber supply device comprises elements including a fiber guide conduit for receiving said bundle of fibers therethrough, fiber-separating means disposed downstream of said fiber guide conduit for receiving said fibers from said guide conduit, and a fiber supply conduit disposed downstream of said fiber-separating means and in communication with a fiber input to said rotor for coupling said fibers from said separating means to said rotor, said elements being arranged so that the speed of said pneumatic flow is a maximum within said fiber supply device at a distance L downstream of a nip point of said bundle of fibers, said distance L being defined as 2/3 l L l wherein l is the average length of said fibers, whereby said fibers are extracted from said bundle of fibers at said point of maximum flow speed, thereby decreasing breakage and unevenness of the yarn.
 3. Spinning apparatus as set forth in claim 2, in which said fiber guide conduit is provided with an upstream opening for receiving said bundle of fibers, said opening having a trumpet shape spreading out in the upstream direction and defined by the expressions m 2d, and D 1.5d, wherein, D represents the inside diameter of the upstream extremity portion of said trumpet shape opening in said guide conduit, d represents the inside diameter of the downstream extremity of said trumpet-shape opening in said guide conduit, and m represents the axial length of said trumpet-shape opening.
 4. In a spinning apparatus comprising a fiber supply device utilizing an airstream for conveying a bundle of fibers supplied from a supply source, while shredding said bundle of fibers into individual fibers; a spinning rotor for accumulating said individual fibers supplied from said fiber supply device upon an inside wall of said rotor while rotating at high speed, said rotor provided with an aperture for taking out yarn produced therein, means for stripping said accumulated fibers from said inside wall of said rotor while rotating said rotor and taking up produced yarn from said rotating rotor through said aperture; an improvement wherein said fiber supply device comprises a fiber guide conduit disposed adjacent to said supply source said fiber guide conduit having a flattened cross section in its upstream portion, fiber-separating means having an upstream inlet disposed to receive fibers from a downstream outlet of said fiber guide conduit, a fiber supply conduit disposed between said fiber-separating means and the inside of said rotor, and means for controlling the speed of said airstream to be at a maximum at a position within said fiber-separating means, said position being spaced downstream from a nip point of said fiber supply device at a distance L defined as l L l wherein, l represents the average fiber length of said fibers.
 5. In a spinning apparatus comprising a fiber supply device utilizing an airstream for conveying a bundle of fibers supplied from a supply source, while shredding said bundle of fibers into individual fibers; a spinning rotor for accumulating said individual fibers supplied from said fiber supply device upon an inside wall of said rotor while rotating at high speed, said rotor provided with an aperture for taking out yarn produced therein, means for stripping said accumulated fibers from said inside wall of said rotor while rotating said rotor and taking up produced yarn from said rotating rotor through said aperture; an improvement wherein said fiber supply device comprises a fiber guide conduit disposed adjacent to said supply source, fiber-separating means having an upstream inlet disposed to receive fibers from a downstream outlet Of said fiber guide conduit, wherein a portion of either of said fiber guide conduit and said fiber-separating means is provided with at least a portion having a flattened cross section in the path of said fibers conveyed by said airstream, a fiber supply conduit disposed between said fiber-separating means and the inside of said rotor, and means for controlling the speed of said airstream to be at a maximum at a position within said fiber-separating means, said position being spaced downstream from a nip point of said fiber supply device at a distance L defined as 2/3 1 L l wherein l represents the average fiber length of said fibers.
 6. In a spinning apparatus comprising a fiber supply device utilizing an airstream for conveying a bundle of fibers supplied from a supply source, while shredding said bundle of fibers into individual fibers; a spinning rotor for accumulating said individual fibers supplied from said fiber supply device upon an inside wall of said rotor while rotating at high speed, said rotor provided with an aperture for taking out yarn produced therein, means for stripping said accumulated fibers from said inside wall of said rotor while rotating said rotor and taking up produced yarn from said rotating rotor through said aperture; an improvement wherein said fiber-supply device comprises a fiber guide conduit disposed adjacent to said supply source, fiber-separating means having an upstream inlet disposed to receive fibers from a downstream outlet of said fiber guide conduit, a fiber-supply conduit disposed between said fiber-separating means and the inside of said rotor wherein an inside wall of said fiber supply device is coated with polytetrafluoroethylene resin, and means for controlling the speed of said airstream to be at a maximum at a position within said fiber separating means, said position being spaced downstream from a nip point of said fiber supply device at a distance L defined as 2/3 l L l wherein, l represents the average fiber length of said fibers. 